The invention concerns a windscreen wiper system, particularly for passenger automobiles, with a wiper arm provided with a swivelling drive and which has on the free end part a pivot bearing for a wiper blade which can be guided essentially parallel over the windscreen, which blade lies approximately parallel to the wiper arm both in a position of rest in the region of the lower edge of the windscreen as well as also in a central working position, and with a control mechanism associated with the swivelling drive, which has a control element fastened to the vehicle for the parallel guiding of the wiper blade and a scanning element associated with the wiper arm that cooperates with the latter.
Such a windscreen wiper system is, for example, derived from U.S. Pat. No. 2,790,195. Its wiper arm contains two spring-loaded toothed racks, which together engage in a gear wheel on which the wiper blade is arranged, and which can be displaced at the free end of the wiper arm in a longitudinal slot. During wiper motion, the two toothed racks slide along two different control curves, each of which forms a flat V and are arranged on a control element fastened to the vehicle. Thus, the two toothed racks are shifted such that the wiper blade rotates and compensates for the wiper arm stroke by its motion in the longitudinal slot, so that it is guided approximately parallelly. The control curves continue vertically downward coupled to the V form, so that in the transfer to the rest position, the toothed racks are shifted such that the position of the wiper blade parallel to the lower edge of the windscreen is obtained.
Since such a windscreen wiper must move out over the wiper swivel region in the resting position, a parallel guiding over the entire width of the windscreen cannot be achieved. There thus remains either outwardly, or, in the case of two wiper arms, centrally, a region which is not swept over.
Wiper blade systems, in which the wiper blade, in the conventional manner, is maintained constantly approximately parallel to the swivelling wiper arm, which lengthens and then shortens again with increasing swivelling angle on both sides of the central position by means of a control mechanism in order to better sweep over the windscreen corner region, are known in various embodiments (U.S. Pat. No. A 4,447,928, German A 33 15 126, German A 34 11 160, EP A 218,192, EP A 236,757, German A 36 27 035, German A 34 35 475, German A 34 16 466, etc.). A parallel guiding of the wiper blade, however, is not given in any of these embodiments. The latter would, however, be favorable, since a swivelling wiper blade must swivel against the air flow applied to the vehicle and can thus lift off, particularly at high speeds.
Another parallelly guided wiper blade, for example, is known from German OS 36 41 551. The wiper blade there is coupled to two swivelling wiper arms, whose so-called effective lengths are varied during the swivelling motion, so that the wiper blade sweeps over an essentially rectangular field. In one embodiment, the length change of the wiper arm is thus effected by a crank mechanism, coupled to the swivelling drive, and this pushes the wiper arm in and out of a guide that swivels with it. In the rest position, the wiper blade lies laterally along the windscreen frame, whereby the wiper arm must extend obliquely outward over a lower edge of the windscreen. A transfer of the wiper arm together with the wiper blade to a rest position at the lower edge of the windscreen, or below the windscreen, however, is not possible.
German A 28 40 203 shows a windscreen wiper system, in which the swivelling wiper arm, to which the wiper blade is attached in a non-rotatable and approximately parallel manner, is positioned in a rotatable block eccentric to its axis of rotation. The wiper arm can be swung further from its outermost wiper position to a position of rest by means of an adjusting drive. This embodiment, however, has no possible means for parallel guiding.